Primary finding
Probable cause
The pilot's inadequate preflight performance calculations which resulted in an aborted takeoff and collision with trees.
Investigator assessment
Analysis narrative
The pilot reported that, while taking off from a remote mountainous site, the helicopter encountered some turbulent air and the main rotor RPM decayed. He elected to abort the takeoff and land at a site about 20-30 ft from the original location. During the landing, the main rotor blades struck a tree. The helicopter sustained substantial damage to main rotor blades and main rotor hub assembly. The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. He also reported that the accident could have been avoided by taking more time to calculate and determine the density altitude and out of ground effect performance of the helicopter at the time of the accident.